Lecture 5 Flashcards
Organisation of the PNS (29 cards)
What are the main functions of the peripheral nervous system (PNS)?
• Deliver sensory information from the periphery to the CNS
• Deliver motor commands from the CNS to muscles and glands
What is the difference between a nerve and a tract?
• Nerve: bundle of axons in the PNS
• Tract: bundle of axons in the CNS
What are the connective tissue layers of a peripheral nerve?
- Endoneurium – surrounds individual axons
- Perineurium – surrounds fascicles
- Epineurium – surrounds the entire nerve
What are the main glial cells in the PNS?
Schwann cells (myelinating and non-myelinating)
What is the function of Schwann cells?
• Myelinating Schwann cells insulate axons to increase conduction speed
• Non-myelinating Schwann cells support and protect axons
What are the three types of sensory receptors in the PNS?
• Exteroceptors: skin (touch, pressure, temperature, pain)
• Proprioceptors: muscles, tendons, joints (body position)
• Interoceptors: viscera (internal environment)
Where are the cell bodies of primary sensory neurons located?
In ganglia (e.g., dorsal root ganglia or cranial nerve ganglia)
What are the two types of motor systems in the PNS?
• Somatic: voluntary control of skeletal muscle
• Visceral (autonomic): involuntary control of smooth/cardiac muscle and glands
What is a neuromuscular junction?
The synapse between a lower motor neuron and a skeletal muscle fiber
What is the basic structure of a reflex arc?
- Sensory receptor
- Afferent neuron
- Integration center (spinal cord or brainstem)
- Efferent neuron
- Effector (muscle or gland)
What are the two divisions of the ANS?
• Sympathetic: fight or flight
• Parasympathetic: rest and digest
How many neurons are involved in autonomic motor pathways?
Two:
1. Preganglionic neuron (CNS)
2. Postganglionic neuron (PNS, in autonomic ganglia)
What is the difference between a root and a ramus?
- Root: either sensory (dorsal) or motor (ventral)
- Ramus: mixed (both sensory and motor)
What are the four major spinal nerve plexuses?
- Cervical (C1–C5): neck, diaphragm
- Brachial (C5–T1): arm and hand
- Lumbar (L1–L4): abdomen, genitals, thigh
- Sacral (L4–S4): thigh, lower leg, foot
How many cranial nerves are there?
12 pairs
What is the mnemonic for cranial nerve names?
Oh Oh Oh To Touch And Feel Very Green Vegetables AH
(I–XII: Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Accessory, Hypoglossal)
What is the mnemonic for cranial nerve functions?
Some Say Marry Money But My Brother Says Big Brains Matter More
(S = Sensory, M = Motor, B = Both)
CN I – Olfactory
Cortex
- Special sensory – Smell
CN II – Optic
Thalamus
- Special sensory – Vision
CN III – Oculomotor
Midbrain
- Motor – Eye movement (upward, downward, inward, up-&-out)
- Autonomic – pupil constriction and lens accommodation
CN IV – Trochlear
Midbrain
Motor – Eye movement (down-&-in)
CN V – Trigeminal
Pons
- Ophthalmic (sensory) – Scalp and upper face
- Maxillary (sensory) – Nasal cavity and midface
- Mandibular (sensory & motor) – Oral cavity, lower face and chewing muscles
CN VI – Abducens
Pontine-Medulla Border
Motor – Eye movement (lateral)
CN VII – Facial
Pontine-Medulla Border
- Motor – Facial expression
- Autonomic – Salivary and tear glands
- Special sensory – Taste (anterior 2/3 tongue)
